Journal of Integer Sequences, Vol. 20 (2017), Article 17.1.5

Touchard's Drunkard

Nachum Dershowitz
School of Computer Science
Tel Aviv University
Ramat Aviv


Based on Touchard's identity, we give a simple derivation for the enumeration of the N/S/E/W walks that remain on the north side of the origin.

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(Concerned with sequences A000079 A000108 A000244 A000302 A000891 A000984 A001006 A001405 A001700 A002212 A002426 A002894 A002896 A005566 A005568 A005572 A005773 A018224 A026375 A064037 A081671 A138547 A145847 A145867 A150500 A202814.)

Received March 15 2016; revised versions received June 1 2016; December 18 2016; December 21 2016. Published in Journal of Integer Sequences, December 26 2016.

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